98 K1500 Running rough in closed loop?

[narojo]

Rebuilt engine and remanufactured Trans. A lot of new parts under the hood. It's running lean and rough, though. Starts up and idles fine for a bit, rough acceleration at times, and it stalls at most stops. P0452, P0300, P0308, P0174. The spark plugs were all dry fouled when I got it. The previous owner said that the truck appears to run rough in closed loop only, and that he could drive it around just fine with it forced open with his computer. He tried swapping the ECM but it did the same shit. I think there could be a vacuum leak, but I'm not finding one. Sprayed carburetor cleaner all over, blew cigar smoke in the intake, tried to blow myself up.. couldn't find a leak anywhere. What else could it be?

 

Here's some other stuff I've checked/replaced:

Fuel pressure holds pretty steady at 58-60psi

New battery

Fresh oil change

New spark plugs

New PCV and IAC

[CadillacLuke24]

I would be highly suspect of a vacuum leak as well, P0174 is Bank 2 Lean. Are the intake gaskets on that side good? Anything wrong with the intake manifold?

 

How are the spark plug wires? 

 

Cylinder 8 is misfiring, is the fuel injector good? They should have a consistent tick when you listen with a mechanic's stethoscope. I would definitely check cylinder 8 out completely, you'd be surprised at how bad one cylinder can throw things off. 

[riverbanks]

Bad poppet on 8?try some techron fuel cleaner,how old is the spider?

[narojo]

According to the guy that rebuilt the engine, the spider is pretty new. Not sure what happened on cyl 8. I cracked the old spark plug trying to get it out though. Like it was crossthreaded or something. The misfire didn't happen until after I did the spark plugs. I sprayed carb cleaner everywhere and couldn't find signs of a vacuum leak. Was told if there is a leak anywhere it might be on the back intake manifold, the one without a plenum - I didn't know what he was talking about though.. I only see the one intake manifold. He also mentioned some connector or sensor coming off the evap under the hood. I could not find the disconnected wire he mentioned.

 

I put some sea foam in the gas tank a couple days ago.

[riverbanks]

You could have hurt the plug wire on 8,one test I do is a spray bottle with water, lightly mist wire and plug,watch for arcing from wire and evaporation off of plug,then do the same on another cylinder,if a big difference,bad plug, cracked, meaning it's cold,no fire

[narojo]

Thanks I'll give that a shot. I remember hearing the misfire on a test drive. I was going up a hill and it started running rough. I floored it up to around 3000rpm and that's when I heard a lot of backfiring and things. As far as the running lean, my neighbor said he'd bring his computer home from work to scan it today. Hope he does... I'm about ready to throw in the towel trying to figure it out.

[riverbanks]

Another,you could have a bad 02,a easy check is to swap them side to side,see if code stays or follows

[riverbanks]

Another,with the backfiring,bad cap and rotor,they are a two piece cap,molded over the terminals,some are junk

[narojo]

My cousin thinks it might be bad distributor cap/rotor from what I told him, but he hasn't looked at it. The throttle is very loud and sounds like a vacuum leak, but was told that's pretty normal for these trucks. Was told the O2 sensors are new, but I found out from someone else that anything other than OEM sensors is garbage that won't work.

[riverbanks]

We are in a world of "maybe"now,some good,some bad,now with it running better in open loop,it's relying on base perameters,the pcm,that is,now,closed loop,it's getting bad info from a sensor, swap the o2's?

[narojo]

My neighbor mentioned he has a scanner computer at work and will bring it home. If he does, I'll report back with the data. If not, then I will try swapping some sensors and see if that works

[narojo]

Had a friend come over to look at it, he didn't find a vacuum leak either. He thinks it is probably something with the fuel pump. Said a new spider fuel pumps can fail for just having less than a quarter tank of gas. He got it idling okay after messing around with some unplugged sensors ahead of the gas tank. Any idea what those would go to? They are along the driver side. He thinks they are for the exhaust, which has been dropped to a straight pipe. We noticed that the engine also started burning oil as well.

[riverbanks]

Post a picture?of sensors in question

[narojo]

Here's a shot

[narojo]

I finally got my OBDLink. Maf is reading constant 0 lb/min. Tried swapping mine with a friend's too. Supply voltage is 5v with engine off, ground is good. Not sure how to test signal wire - but is it safe to say it's the wire since we tried with my friend's MAF?